Greenacres farm in Hawarden is fab, but take your own food, the cafe is rubbish.
Oh and beware of the piglets! My mum got bitten by one.
Other than that it's great, my ds loved it, we went in the summer and he still talks about it all the time.
Oh and you have to pay to go in the soft play area so I wouldn't bother. However, the tractor ride is well worth it and only costs a quid.